1. Field of the invention
This invention relates to a thin-film, perpendicular magnetic recording and reproducing head.
2. Description of the prior art
Thin-film, perpendicular magnetic recording and reproducing heads have a high frequency response, and due to advances in semiconductor technology, highly accurate thin-film magnetic heads can be manufactured at a low cost. It is expected that they will soon be used more commonly than any other type of presently known magnetic head.
Thin-film, perpendicular magnetic recording and reproducing heads are generally classified into inductive heads, which are used for recording and reproducing purposes, and magnetic resistance heads, which are used for reproducing purposes. An inductive head comprises a magnetic substrate which is formed from, e.g., soft ferrite; an insulating layer provided on the magnetic substrate, this insulating layer containing a thin-film conductor; a main pole provided on the insulating layer and formed from, e.g., Permalloy, Sendust or a amorphous alloy; and a protective overcoat covering the main pole. These thin-film, perpendicular magnetic recording and reproducing heads are usually manufactured by a process as follows:
(a) Forming a plurality of grooves in a predetermined pattern in a principal surface of a magnetic material, filling these grooves with a nonmagnetic material, such as glass, SiO.sub.2, Al.sub.2 O.sub.3 or barium titanate, and then finely polishing the principal surface of the so-formed magnetic substrate.
(b) Forming a thin-film conductor coil on the polished principal surface of the magnetic substrate, and then forming an insulating layer on the magnetic substrate and the conductor coil, the insulating layer consisting of a film of either an organic material such as a resist or polyamide, or an inorganic oxide such as SiO.sub.2.
(c) Flattening the exposed surface of the insulating layer which is uneven (it will have an uneven surface due to the presence of the conductor coil on the magnetic substrate) by an etchback method employing a resist, which is described, for example, in Technical Report US 86-13 of the Institute of Electrical Communication Engineers of Japan.
(d) Forming a via hole in the insulating layer so as to provide for magnetic contact between a subsequently formed main pole and the magnetic substrate.
(e) Forming a main pole on the surface of the insulating layer and the exposed surface of the magnetic substrate, and after subsequently forming a magnetic film and a protective overcoat on the main pole, cutting the assembly to a predetermined size and then polishing it.
The magnetic properties of the main pole in the thin-film, perpendicular magnetic recording and reproducing head manufactured as just described usually depend on the nature of the surfaces of the insulating layer and the magnetic substrate, including roughness and residual stress. Unfortunately, the etchback method is not effective for satisfactorily flattening the surface of the insulating layer, e.g., when it is composed of an inorganic oxide. As such, it is difficult to obtain a uniform wafer surface by this method. Moreover, it is an inefficient method because it requires a great deal of labor and time.
In addition to the foregoing, the insulating layer has a projecting edge along the surface thereof adjacent to the via hole. As such, that portion of the main pole which covers the projecting edge of the insulating layer will have a reduced and nonuniform film thickness, which lowers the magnetic properties of the main pole and thereby the performance of the magnetic head as a whole.